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The canine guide to lumps and bumps on dogs

Does your dog have a lump or bump on or under their skin? While lumps and bumps are more common in older dogs, younger dogs can get them too.1 Most lumps and bumps are benign (non-cancerous), but some of them can be malignant (cancerous). The older your dog is, the higher their chance of getting malignant lumps. The good news is that early detection and treatment of cancerous lumps can increase the chances of a cure.2

What type of lump or bump is more dangerous? What causes lumps and bumps on dogs, and how can you treat them?

How your vet can tell what type of lump or bump your dog has

Your vet will conduct one or more of the following tests to determine the type of lump or bump your dog has and the treatment required2:

  • Fine needle aspiration (FNA) – Firstly, your vet will determine if this procedure can be performed during the consultation without the use of sedatives. If the vet determines they can use this technique for a diagnosis, a small needle is inserted into the lump to suck out cells which are then deposited onto a slide. Next, the slide is stained and the slide is viewed under a microscope to examine the cells. Your vet may send the slide to a specialist (pathologist) in a laboratory for examination. About 95% of lumps and bumps can be diagnosed via FNA.2
  • Impression smear – If the lump discharges fluid, your vet may rub a slide onto the lump, and then stain it and examine the fluid as with an FNA.
  • Biopsy – If the FNA isn’t diagnostic or only contains blood/fluid, your vet might take a biopsy of the lump. Generally, your dog will receive a sedative or anaesthetic and a small part of the lump or the entire lump will be removed. Then the lump is placed in formalin and sent to a lab, where thin sections of the lump are examined under a microscope.
  • Lab test – If the lump contains fluid, the fluid could be sent to a lab to culture and check for infectious agents like fungi or bacteria.

Types of lumps and bumps – benign vs malignant

Benign (non-cancerous) lumps and bumps

Benign lumps and bumps lack the ability to invade other tissues and spread to sites beyond where they are present. The vast majority cause little concern, however those that continue to grow can cause problems, like restricting movement or breathing because of the lump’s size, or your dog keeps scratching them because they’re irritating. If benign lumps are causing problems, removal should be considered.1

Lipomas (fatty lumps)

Lipomas are the most common benign mass dogs can get; they’re often found under the skin of older dogs3, and are more common in obese dogs.1 They tend to be round, soft tumours of fat cells that grow very slowly and rarely spread1, so it can take up to six months before you see any change3.3 Lipomas can be easily diagnosed with FNA.

If they become very big or hinder movement (e.g. growing behind a leg or in the armpits), your vet might recommend removal.3

Abscesses

Abscesses are swollen lumps that contain an accumulation of pus under the skin caused by an infectious agent. They will generally need to be drained under sedation and copiously flushed with a clean antibacterial solution. In some cases, your vet will prescribe antibiotics if they deem it necessary.

Hives (urticaria)

Hives on dogs are similar to those on humans – a rash of round, red weals on the skin that itch and swell due to a reaction of the skin to allergens such as a bee sting or contact allergy. They will often resolve on their own, however sometimes they need steroids or antihistamines to provide relief.2

Sebaceous cysts

Sebaceous cysts are hard, cystic material under the skin that can form due to a blocked sebaceous gland.3 They appear like swellings with a creamy matter inside them. The swellings sometimes become red and sore. They’re usually found in older dogs in the middle of their back and can be diagnosed with FNA.1 Most of them don’t cause problems, so they’re usually left alone unless they’re infected or irritate your dog.3

Histiocytomas

Histiocytomas are an ulcerated nodule (or red button-like lump)2 often found in young dogs, particularly on their limbs. They normally go away quite quickly but you should still have them checked by your vet as they can imitate some very nasty cancerous tumours.

Sebaceous adenomas

Sebaceous adenomas are tumours of sebaceous glands that appear as multiple wart-like growths. They’re more common in woolly-haired older dogs like Poodles, Maltese, Bichons, and their crossbreeds.2 A biopsy is required for diagnosis but vets can often diagnose these lumps by just looking at them due to their classic appearance and slow growth. Most of them don’t cause problems, but those that are ulcerated, irritate your dog, or are being licked or chewed at by your dog should be removed.3

Perianal adenomas

Perianal adenomas are tumours that grow around the anus, mostly in non-desexed older dogs. Any lump or bump around the anal region requires proper assessment and investigation due to malignant tumours in this area being common.

Warts

Warts are more common in puppies, older dogs and dogs that are immunocompromised, and look like small skin tags or several small lumps. They’re usually found on the head and face and are caused by a papillomavirus. Dogs that go to a doggy daycare or dog parks can get warts due to close social contact with other dogs. A biopsy is required for diagnosis but vets can tell due to their classic feathery appearance. No treatment is necessary, as they’ll usually go away by themselves after a few months.3 However, they can irritate your dog, and if this occurs removal should be considered.1

Granulomas

Granulomas can be raised red lumps that may have a surface crust, or they can be found under the skin and have a firm consistency. They’re often not adhered to muscle. They can look similar to a highly aggressive tumour so vets will usually recommend a biopsy/surgical removal or FNA. Surgical excision is often required for treatment.

Haemangiomas

Haemangiomas are tumours of blood vessels or underlying tissues of the skin. Sun exposure can lead to their development, however this isn’t always the case. Diagnosis is done by a biopsy or surgical excision with the sample being tested by a pathologist. This is always recommended as these tumours can change over time to become malignant. Surgical excision is curative if the tumour is benign.

Malignant (cancerous) lumps and bumps

Malignant lumps and bumps grow and can spread through the body and affect organs like the liver and lungs1, along with the brain and bones. They can spread by local growth (destroy nearby tissues) or by metastasis (tumour cells enter the bloodstream or lymphatic system to spread to other body sites). It’s important that malignant lumps and bumps on your dog are surgically removed as soon as they’re diagnosed to keep them from spreading and causing devastating consequences. Chemotherapy and radiation therapy are also often used to prevent further spread.

Mast cell tumours

Mast cell tumours are a tumour of the immune system blood cells, and comprise of up to 25% of all tumours. They’re most common in dogs older than 8 years of age. Mast cell tumours can look like many other tumours, so it’s vital to have them diagnosed accurately by a vet. Usually vets will start with a FNA. When diagnosed, it’s important to check if the tumours have spread to other organ systems.

Fibrosarcomas (soft tissue sarcomas)

Fibrosarcomas are locally invasive tumours of the skin’s connective tissue that grow fast. They’re common in large breeds. A biopsy is required for diagnosis, as they feel like lipomas and can be mistaken for them if FNA isn’t done.3 They usually spread by local invasion2 and can be difficult to remove, as prompt, careful resection with a wide surgical margin is required.3

Melanomas

Melanomas in dogs are not caused by sunlight and are a lot less malignant than human melanomas.3 Canine melanomas are tumours involving cells that give pigment to the skin. They can be benign or malignant2 and appear as dark lumps on the skin that grow slowly.3 More aggressive tumours grow on the mouth and legs.2 They have to be removed but they can recur.3

Squamous cell carcinomas

Squamous cell carcinomas are skin cell tumours found on unpigmented or hairless areas such as the eyelids, vulva, lips and nose, and present as raised, crusty sores. It’s another tumour caused by too much sun exposure.2

They usually grow by local invasion and should be removed.2 If they’re left for too long, they can cause great deformities and pain, as well as spread to lymph nodes and other organs, ultimately resulting in death.3

Mammary carcinomas (breast cancer)

Mammary carcinomas are cancerous growths of the mammary glands. They’re more common in non-desexed female dogs.2 Lumps in the mammary glands can be benign, however it’s worth noting that mammary tumours in male dogs are often always malignant. They spread by metastasis to the lymph nodes, other mammary glands and organs. In most cases, it’s recommended that you get mammary lumps surgically removed1, and chemotherapy is an option after removal.

Osteosarcomas

Osteosarcomas are the most common bone tumour, especially in large male dogs. They’re caused by abnormal bone cell growth, unusual hormone stimulation, a previous fracture in the area, or genetic factors.4 They can cause bumps or lumps to form in the bone, usually in the limbs, and often spread to the lungs by metastasis. They’re diagnosed with biopsy and lab tests of bone and skin tissue. They need surgical removal, which may include amputation of the affected limb.4

Chondrosarcomas

Chondrosarcomas are the second most common bone tumour and usually occurs inside of the nose. They’re also caused by abnormal bone cell growth, unusual hormone stimulation, or genetic factors. A biopsy and lab tests of bone and skin tissue are also required for diagnosis.

Treatment of nearly all malignant tumours requires surgical excision and chemotherapy and/or radiation. When a lump or bump is diagnosed as malignant, your vet will want to x-ray other areas and/or ultrasound the abdomen to determine if the tumour has metastasised. In some circumstances, the vet will recommend a CT examination to determine exactly where in the body the malignant cells are. This is called staging.

Other things that cause lumps and bumps on dogs

Ticks

Causes

Your dog can get ticks if you take them for a walk in bush areas or scrub areas that harbour ticks. Ticks can also reside in tall lawns and shrubs and in compost material in your backyard. Depending on where you’re located, your pet may be exposed to the paralysis tick, brown tick or kangaroo tick. It’s very important that you learn to differentiate between the different types of ticks prevalent in your area, and that you’re alert for clinical signs of their presence on your pet. Consult with your vet for advice on what ticks are prevalent in your area, and what signs to look for.

Diagnosis

When a tick attaches themselves to your dog, they’ll suck blood from them and a red crater appears on the skin afterwards. A tick crater is proof that a tick was attached to your dog. Tick craters can be felt as lumps on the surface of the skin. Most ticks will attach to the face, neck, and ears, but they can also attach to other areas of the body.5

Treatment

If you see a tick crater on your dog’s skin, search their entire body for ticks and remove them as fast as possible. Paralysis ticks are life-threatening, so if you notice a change in your dog’s behaviour, ability to walk, voice, breathing, vomiting or regurgitation and you live in a paralysis tick area, please visit your vet immediately. The best way to avoid your dog getting ticks is to use tick preventatives year round. Check your dog daily for tick craters and bumps by running your hands over their body, paying particular attention to their neck, ears, under their collar and between their paws.

More treatment options available for your dog

Depending on the type of lump or bump your dog has, its location and size, and the characteristics of your dog, more treatment options are available, including:

  • lumpectomy for benign and early malignant lumps and bumps. This is the surgical removal of the lump. Sometimes a very large incision is required to ensure that all potential cells are removed. This is called ‘clean edges’.
  • partial removal or debulking for lumps and bumps that can’t be completely removed.
  • cryosurgery for benign lumps and bumps. This is when extreme cold (liquid nitrogen) is used to remove very superficial skin lesions.
  • radiation therapy for malignant lumps and bumps that can’t be surgically removed or when surgical removal will cause unacceptable physical impairment. It uses high energy radiation to shrink or kill cancer cells, and is often used when surgery isn’t an option or after surgery to mop up any remaining cells.
  • chemotherapy for malignant lumps and bumps and in addition to surgery or radiation therapy.6 Chemotherapy is the use of drugs to kill cancer cells in the whole of the body. It’s used to treat cancers of the blood and lymph systems, and to mop up cells after surgical removal.

Other types of therapy that can be used to treat lumps and bumps on your dog include:

  • hyperthermia
  • laser therapy
  • photodynamic therapy
  • antiangiogenic therapy
  • metronomic therapy
  • gene therapy
  • immunotherapy
  • multimodal therapy (uses a combination or sequencing of different therapies)6

An area of concern for many pet owners when dealing with treatment for lumps and bumps on canines is the cost involved. Having Pet Insurance in place from an early age before signs or symptoms appear can assist with alleviating the financial stress associated with having a sick dog, as pre-existing conditions will usually be an exclusion on a policy. Visit our RSPCA Dog Insurance page for more details on how Pet Insurance may assist you, or get an obligation-free quote here.

Now… what should you do?

Maintaining the health of your dog’s skin and coat is vital to preventing certain skin conditions such as lumps and bumps. But if your dog has a lump or bump, get it checked by your local vet straight away. They can tell you whether it’s dangerous or not and the best way to treat it. If your dog doesn’t have any lumps or bumps, you should check them on a regular basis so you’ll notice any changes that occur. Run your fingers through their coat and if you feel a lump or bump, take them to your vet for immediate examination.

The earlier a lump or bump is diagnosed, the more successful the treatment will likely be.1

Author

Dr Leigh Davidson, BVSc, BApplSc, has over 17 years’ experience as a vet, and is the founder of Your Vet Online. Your Vet Online provides animal owners who have animal health queries 24 hour online access to registered veterinarians, 365 days a year.